Pavement for highways



Patented Oct. 13, 1925.

EIMER o. HooPnR, ornnw road, at. Y.

PAVEMENT FOR HIGHWAYS.

Application filed November 1, 1922. Serial No. 5983M.

T all whom it may concern Be it known that 1, ELMER G. HOOPER, citizen of the United States of America, residing at 420 East 239th Street, New York city, in the county of Bronx and State of New York, have invented certain new and useful Improvements in Pavement for High ways, of which the following is a specification.

This invention relates to highways, and has special reference to a pavement for highways.

It is to be understood that the use of the terms highways and pavement throughout this specification and claims are not to be restricted to the precise definition of these words, but the termfhighways is to be read as sufliciently broad to cover all roadways, courtyards, and other like places both public and restricted which are intended primarily to carry vehicular traflic. Also the term \pavement as' used herein is to be read throughout as broad enough to cover not only the surface on which the traflic passes,

2 but the substructure or artificial permanent foundation on which may be laid surface.

In order that the purpose of the invention may be clearly appreciated, it is expedient to explain briefly the requirements of the modern highway. Because of the great developments of the motor vehicle, and the intensive use of the same in transportation over the highways and roads the requirement has arisen for permanent, hard, smooth pavements for such highways. The developments of the motor units in number, weight and speed has been such that the design and construction of highway surfaces, to fulfill the 4') above requirements, has not kept pace. Among the reasons for the present lack of developments of highway surfaces or pavements has been the fact that the soil usually met with on or near a highway has not, as a rule, been found susceptible to treatment that would satisfy the requirement of permanency, and in consequence, it has been the practice to design some artificial structure having a limited ability to resist the rupture from stretching or compressing and to place such structure upon the natural ground, prepared or treated, to a greater or less degree, to support it.

When such an artificial structure is first placed upon the ground, assuming that the proper care has been taken, it is most probably uniformly supported. throughout and conforms in shape to the soil surface as prepared for the structure. is found to last but a short time with the result that the structure is subjected to stresses different in kind and amount than those for which it was intended. The mag nitude of such stresses cannot be predetermined because of the fact that moisture and temperature conditions cause very wide variations in the action of the soils beneath theartificial surfaces or pavements. For instance, moisture'run's off of the structure, soaks into the soil along the edges, and

with soil thus moistened a certain expansion takes place which tends to lift the structure by the edges so that the sustaining of the structure by the soil at the middle is lessened, and the tendency is for the structure to sag at the middle thus compressing the surface and stretching the underpart. Furthermore, other conditions may arise wherein the surface structure or pavement will be supported principally at the middle, and thus there will be a tendency to sag on the edges with consequent stretching of the upper part of the pavement and compression of the lower. Obviously, if either of these conditions prevail, the weight of a motor vehicle and its load This condition running over such pavement produces rapid disintegration of the pavement structure.

I-leretofore it has been customary to so design the pavement structure that the intent is to support the same throughout its entire length and breadth, and it has been also customary, especially in precasting or forming pavement structures, to form such structures as rectangular blocks or sheets,

and to pay especial attention to the support of the same at the corners. Under such conditions,'if the support at any corner is lessened, it IS impossible, in practice, to

determine what stresses will be brought by arranged that 0,111

a load at any portion of the slab or pavement. If, however, the structure be designed to rest onthree supports, moderate settlement of any or all of them will all'ect the stresses to only a slight degree.

One important object of the invention is to provide a novel form of highway surface or pavement to which is applied, in the design, this principle of three supports, the

invention also contemplating the construc tion of reenforced concrete slab units or slab units of other rigid material so designed as to render themselves readily to a three point support.

In a preferred embodiment of the invention, the slabs referred to are given the formation of triangles of substantial size such that two or three or other small number of slab units extends across the full width of the roadway. By arranging such slabs in an edge to vedge formation with a rigid support at the apices it will be seen that I obtain the full advantage as to stability arising out of the three-point-support such as is typified by the well known threelegged-stool effect. The arrangement of the slabs in the edge to edge relation referred to gives rise to the grouping of six apices of as man 1 slabs at a common point so that but a sing e support is needed for the group.

The term point as used throughout the case is intended to mean a surface or area that is relatively small as compared with the superficial area of one of the paving slabs. For instance as disclosed in the drawing a pointrepresents the area of contact between a slab and the top of a supporting post, pile or other support presenting a relativel small area of contacting engagement with the slab. The term line in the same connection is intended'to mean an area of relatively great length as compared to its width as illustrated by the top edge of a beam, curb or the like.

The expression three-pomt-support is therefore intended to mean the support of pavement units or slabs on three points so two of the points liein the same vertica plane.

the point supports by a line support so that the three-point-support is intended to in clude'support on one line and onepoint not in the same vertical plane withithe line.

i In this respect, it is to be understood that by. a three point support of such a device 'as'a triangular slab the term three point support or other 7 like term is not to be taken literally throughout this specification,

but-is to'be understood as broad enough to include also the support of a triangular slab along one edge and at the opposite angle,

this being the full equivalent, for the pur pose, of a three point support. Consequent- Similar results may also be obtained by replacing two-of 1y, when such term is used in the specification and claims, it is to be read as broad enough to include both forms.

Even though the settlement of such three point supports may not seriously increase the stresses in the slabs, such settlement of a single support would tend to make the general pavement surface warped at joints and unpleasant to ride over.

A second important object of the invention is to provide an improved construction of highway pavement wherein .the latter Wlll be supported on suitable posts or piles of concrete, plain or reenforced with metal,

metal, or other solid and durable material, placed upon, or drlven to a 5011 stratum of satisfactory bearing power, at or below the so-called frost level, or to solid rock, the posts or piles being so arranged as to act as supports for the slabs to rest upon.

A third important object of the invention is to provide suitable means for connectingthe slabs to the supporting posts, such means being so designed and arranged as to permit only slight lateral movement for temperature changes, but freely permitting the jacking or raising of the slabs off of the supports, and placin of so-called shims in order to level up t e pavement in the event tion is to provide, in such a pavement, interlockingjoints, so designed as to lock the adjacent slabs together along their edges,

and thus make adjoining edges sag equally or approximately the same amount. This from a given load, and consequently, will enable economy to be effected in design.

fifth important object of the invention is to provide for the precasting, in molds, of the separate slab units'and to have them placed in position on the pavement foundawill cause a wider distribution of stresses tionafter proper seasoning. This method will permit makingan-d storing of slabs in shelter'so workmay be continued on this part during storm and bad weather. It will permit rapid laying of slabs and causeless interruption of traffic, to allow seasoning.

Thus transportation of the slabs from the central yard to their final osition may be over the finished surface as ast as the latter is laid. Spare slabs may be kept in stock for replacement, since it is; the intent that line 33 of Fig. 1;

pins used hercwit Fig. 5 is a detail view showing the connec-'- tion of one of the slabs to one ofits su porting posts;

Fig. 6 1s a view showing portions of two the design of dowels and lock joints is such acters of reference indicate like parts in the several views, and

Fig. 1 is a plan View of a section ofa pavement constructed in accordance with this invention; Fig. 2 is a units of such a avement;

Fig. 3 is an enlarged Fig.4 is a detail view of adjoining slabs at one of the angles of the triangle. q In carrying out the invention, there is Afirst of all provided a series of piles or posts 10,-which are preferably placed with their centers at 'the corners of triangles. In the central art of the pavement these posts are p'referalily circular in cross section, al-

though they may be hexagonal or any other convenient shape, the ob ect being to pro vide for the support of the anglesof six slabs. At the ed es of the pavement, the

. posts are prefers. 1y semi-circular in cross their corners with dowel lugs 14 wheremare section so as to' support three ad'acent angular portions of the slabs. Eac of these posts-in the center is provided with six owel pin receiving 0 enings 11 wherein lit the dowel pins 12. t the sides, there are of these dowel pin regeneral triangular form, as shown at 13, the slabs pin receiving openof the pins 12'. Furthermore, e edge of each slab 'is' provided at its 1 upper or its "lower surfacewith a recess 15,.adjacent'to -1Which is a prdecting li 16, theli of one slab fitting the rece'ss'o theadjacent slab. By this means the slabs" are given a three point support and adjacent slabs are locked 3 together sothat any depression of anedge of one ofthesc slabs will adjacent edge of the next, slab thus distrib--' tend to'depress the methods of calculation, data,

detail section onth'e' one of the dowel tension.

. crete in most unit, considered of slab receiving position'of said loadexl being provided at received the pm. ends It is expedient to givea typical design of u a single slab unit, of reinforced concrete, illustrative of the method proposed. The

and arrangement of material used is reasonably justified by present day knowledge of principles and of facts, but by use of said method of calculation, data and arrangement of ma terial, it is not intended to limit the design,

since it is hoped that more experience and v experiment may show ways of improvement. perspective view of one of the ,slab and its The claims made with reference to design of placing are basic and are not afi'ected by c ange in data or in arrangement ofmaterial.

It is (proposed to place steel in such position an in such quantity as to take 11 all Concrete of fine quality wil be used. to take up compressive stresses. Concases is suliicient to care for shear but some'rods may be bent to take diagonal 'tension.

Inasmuch as simplicity of construction methods is necessary for economy, the slab for calculation, is taken of uniform thickness throughout, and the critical section, as at the middle of the ed e no support from an adjacent one, that IS, the ed e next the shoulder of the road. The loa the weight of a loaded truck, totalling thirty thousand pounds, increased by twenty five per cent-for impact; thirty five percent of this is carried by each rear wheel'spacedsix feet aparton centers'of thirteen inchtreads corresponds to the.

e present day. The truck for maximum at the critical section abovere ferred to, gives a loading of thirteen thou one hundred i pounds at that section,

or tires. 7 This loadin maximum allowed at t ending,

sand Stresses in steelreinforcing are considered ing considered is safe up to the elastic limit but some value?- under-that, say thirty thousand pounds per square inch, is preferred, in order that deflections may i not be excessive. concrete are considered safewhen not ex- Stresses in ceeding sixty Per cent of the ultirhate strength, "that is, for concrete having an ultimate strength of thirty five hundred pounds per square inch after twenty eight days, an indefinitely stress up to twenty one hundred pounds per 1 square inchis allowed. For the values of allowed stress, noted above, a design having pne and one quarter per cent reinforcement is safe when the computed steel stresses are repeated compressive satisfactory, since stresses in the concrete will vtall below that allowed.

The nomenclature adopted is quite commonly used, and, where not specifically defined, is considered as having a meaning given, or implied, in the text book Principles of Reinforced Concrete Construction by T urneaure and Mauror.

P, ratio of steel area to effective concrete area 0.0125 a, ratio of moduli of elasticity,

steel to concrete 12. 1', ratio of allowable to maximum concrete stress 0.60 rl, effective thickness of slab 6 0 in. D, total thickness of slab 7. Din.

I 1. m =pd js a 2 l in M1 3 4250 as5 12 3 x 2 7), efiective breadth of slab acting as a beam at a given time.

IV wheel load plus impact W weight of slab unit M, maximum live load bending moment. 7

.\'l,, maximum dead load bending moment.

2:1,, resisting moment of slab per inch. width.

m resisting moment of slab per inch Width effective againts live load bending moment.

13100. 0 lbs. 4250. 0 lbs.

Z, unsupported span, or beam length 8. 85

X 36 X .85 X 30,000 11,480 inch pounds.

75,300 inch pounds.

Width of cross section to resist M 72". Dead load moment per inch Width- 1040 inc.

3. m 11,480 1040 10,440 inch pounds.

The calculations are not complete, out are sufiicient to show approximate methods. Because a new invention is dealt with, the application of old principles to the design must necessarily be susceptible of correction or adjustment after experience and experiment show the Way.

From the foregoing it will be seen that a highly effective pavement is. provided, which may be cheaply and economically installed, bearing in mind the permanency and supporting qualitiesof the pavement.

Having thus (l9SC1ll')@tl the invention, what is claimed as new, is: 4 1. In a pavement ot' the class described, a series of supporting posts arranged at the apices of triangles, and-supporting slabs of triangular form having their apices resting on said supporting posts.

2. In a pavement ot' the class described, a series of supporting posts arranged at the apices of triangles, supporting slabs of triangular form having their apices resting on 348,000 inch pounds.

3. In a pavement of the class described,

a series of supporting posts arranged at the apices of triangles, loose dowel pins extending upward from-said posts, and triangular formed slabs resting on said posts at their angles, and having openings therein to receive said dowel pins.

4. In a pavement of the class described, a series of triangular slabs arranged edge to edge, the apices of the triangles of adjacent slabs meeting in a common point, and supporting means in said apices, said slabs being interlocked along their edges to prevent independent vertical movement.

5. In a pavement of the class described, a series of supporting posts arranged at the apices of triangles, supporting slabs of triangular form having their apices resting on said supporting posts, said slabs being interlocked along their edges to prevent independent vertical movement.

6. In a pavement of the class described, a series of supporting posts arranged at the apiees of triangles, supporting slabs of triangular form having their apices resting on said supporting posts. and secured thereto against slipping therefrom, said slabs being interlocked along their edges to prevent independent vertical movement.

7. In a pavement of the class described, a series of supporting posts arranged at the apices of triangles, loose dowel pins extending upward from said posts. triangular formed slabs resting on said posts at their angles and having openings therein to receiv said dowel pins. said slabs being interlocked along their edges to prevent independent vertical movement.

8. In a pavement of the class described, a series of supporting posts arranged at the apices of triangles, loose dowel pins extending upward from said posts, triangular formed slabs resting on said posts at their angles and having openings therein to reoeive said dowel pins, said slabs being inter- 'said lips and recesses forming interlocking means, the angle at the ends of the lips and recesses With the edge of the slab being such that any slab may be removed from look after removal of its'dovvels by a slight lateral movement approximately normal to the free edge of such slab.

In testimony whereof I hereunto atfix'my signature.

ELMER G. HOOPER. 

